Motorcycle exhaust enhancement device

ABSTRACT

Embodiments of the present invention provide an exhaust enhancement device that allows a motorcyclist to achieve a desired engine sound while also achieving improved engine performance by reducing exhaust reversion. More particularly, embodiments of the present invention provide for an exhaust enhancement device having a cylindrical tubular body portion configured to be disposed within a motorcycle exhaust pipe so that exhaust gasses may flow therethrough. The exhaust enhancement device further includes a frustoconical screen extending from an end of the cylindrical tubular body portion. The frustoconical screen has an array of holes in its wall for allowing exhaust gasses to pass therethrough. The exhaust enhancement device may further include one or more washer-like members disposed therein and configured to alter the flow of exhaust gasses so that reversion is reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/005,655 filed Dec. 7, 2004, which in turn is a continuation-in-partof U.S. application Ser. No. 10/408,860 filed Apr. 7, 2003, now U.S.Pat. No. 6,848,252 granted Feb. 1, 2005, which claims priority from U.S.provisional application No. 60/387,005 filed Jun. 6, 2002.

FIELD OF THE INVENTION

Embodiments of the invention relate generally to exhaust enhancementdevices for motorcycles.

BACKGROUND OF THE INVENTION

Motorcyclists are always seeking the right blend of sound andperformance from their motorcycles. Often the sound is inextricablyintertwined with the horsepower and performance of the engine. Forexample, using an aftermarket exhaust pipe to gain horsepower andperformance may change the sound of the motorcycle. Furthermore, manymotorcyclists prefer a particular type of sound for their motorcycle.For example, many motorcyclists try to achieve a “deep,” “rich,” and“throaty” sound. Motorcyclists, however, must also be aware of the manynoise ordinances that have been put in place around the country. Manymotorcyclists have, therefore, strived to create aftermarket exhaustpipes that achieve a proper balance of sound, volume, and performance.It would therefore be desirable to have an exhaust system that producesa quality sound without sacrificing performance. It would also bedesirable to have an exhaust system that produces quality sound andperformance at an acceptable volume level. It would also be desirable ifsuch a device could be adjustable, customizable, or in some waychangeable such that the motorcyclist can change the sound andperformance of the motorcycle depending on the motorcyclists preferencesor intended uses.

BRIEF SUMMARY OF THE INVENTION

In general terms, embodiments of the present invention provide anexhaust enhancement device for a motorcycle exhaust pipe. The exhaustenhancement device may include a cylindrical tubular body portionconfigured to be received within a motorcycle exhaust pipe. The exhaustenhancement device may further include foraminous screen extending fromsaid first end of the cylindrical tubular body portion. The formaniousscreen has a frustoconical configuration converging as it extends awayfrom the body portion to define an open first end of a diametergenerally corresponding to the diameter of said first end of the bodyportion and an open opposite second end of a smaller diameter. At leastone obstruction is positioned within the cylindrical tubular bodyportion or the frustoconical screen in the flow path of exhaust gasespassing through the enhancement device. In some advantageous embodimentsof the invention, the at least one obstruction comprises a flat circularmember oriented in a plane perpendicular to the longitudinal axis of thecylindrical tubular body portion. The flat circular member may suitablyhave a central opening and may be positioned coaxially of thelongitudinal axis of the cylindrical body portion. According to oneexemplary embodiment of the invention, the flat circular member ispositioned within the frustoconical screen. In another exemplaryembodiment, the flat circular member is positioned within the tubularbody portion.

In some embodiments, the exhaust enhancement device has two flatcircular members, one flat circular member positioned within the tubularbody portion and another flat circular member positioned within thefrustoconical screen. In general, the outside diameter of at least aportion of the cylindrical tubular body portion is approximately equalto the inside diameter of the motorcycle exhaust pipe. In oneembodiment, the cylindrical tubular body portion includes areduced-diameter center chamber between its two opposite ends. In suchan embodiment, a flat circular member may be positioned within one ofthe opposing cylindrical ends.

Embodiments of the present invention further provide a motorcycleexhaust system having an exhaust pipe for expelling exhaust from anengine; a cylindrical tubular body portion disposed within the exhaustpipe; a frustoconical screen extending from one end of the cylindricaltubular body portion, the frustoconical screen generally converging asit extends away from the cylindrical tubular body portion, and thefrustoconical screen having at least one opening therethrough; and aflat circular member positioned within the cylindrical tubular bodyportion or the frustoconical screen in the path of the exhaust gasses.The frustoconical screen may extend from the end of the cylindricaltubular body portion generally toward an engine end of the exhaust pipeor may extend from the end of the cylindrical tubular body portiongenerally toward an exit end of the exhaust pipe.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 a schematically illustrates a motorcycle engine with a pair ofexhaust pipes and shows where the exhaust enhancement devices may belocated in the exhaust pipes, in accordance with an embodiment of thepresent invention;

FIG. 1 b schematically illustrates how the exhaust enhancement devicemay be located in the exhaust pipe in accordance with another embodimentof the present invention;

FIGS. 2 a and 2 b illustrate a perspective sectional view and anexploded view, respectively, of an exhaust enhancement device inaccordance with an embodiment of the present invention;

FIGS. 3 a and 3 b illustrate a perspective sectional view and anexploded view, respectively, of an exhaust enhancement device inaccordance with another embodiment of the present invention; and

FIG. 4 is a cross-sectional view of an exhaust pipe having an exhaustenhancement device disposed therein in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the inventions are shown. Indeed, these inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

FIG. 1 a schematically illustrates a motorcycle engine 1 with a pair ofexhaust pipes 2, and shows where the exhaust enhancement devices 10 maybe located in the exhaust pipes 2, in accordance with an embodiment ofthe present invention. As shown in FIG. 1, an exhaust enhancement device10 may be installed inside the motorcycle exhaust pipe 2 proximate itsdischarge end. In general, the exhaust enhancement device 10 includes acylindrical tubular body portion 20 and a frustoconical screen 30. Thecylindrical tubular body portion 20 is generally coupled to thefrustoconical screen 30, and the frustoconical screen 30 generallytapers or “converges” as it extends away from the cylindrical tubularbody portion 20. As used herein and in the claims, the term “conical”refers to conical and frusto-conical shapes, as well as other convergingor funnel-like shapes including funnel-like shapes having polygonalcross-sections. Furthermore, as used herein and in the claims the term“converge” is used to describe the tapering sides of the conical shapeand do not necessarily require that the sides completely merge togetherat a single point in space. In fact, as described herein, in thepreferred embodiments, the sides of the conical portion do notcompletely merge together and in fact terminate at an opening oppositethe base of the conical shape.

FIG. 1 a illustrates the exhaust enhancement device 10 positioned in theexhaust pipe 2 such that the frustoconical screen 30 is on the“downstream” end of the cylindrical tubular body portion 20, which isthe end of the cylindrical tubular body portion 20 positioned closer tothe exit of the exhaust pipe 2. In another embodiment, however, theexhaust enhancement device 10 may be positioned such that thefrustoconical screen 30 is on the “upstream” end of the cylindricaltubular body portion 20, which is the end that is closer to the engineside of the exhaust pipe 2. Such an embodiment is illustrated in FIG. 1b.

In general, embodiments of the exhaust enhancement device 10 create aunique rich and throaty sound at an appealing volume when the exhaustenhancement device 10 is installed in a motorcycle's exhaust pipe 2.However, changing the orientation of the exhaust enhancement device 10from the orientation shown in FIG. 1 a to the orientation shown in FIG.1 b generally changes the sound and the performance of the motorcycle.In this way, the user may use the exhaust enhancement device 10 toproduce at least two different sounds. The user may also be able use theexhaust enhancement device 10 to bring the engine's power band (or“sweet spot”) in at different RPMs simply by reversing the exhaustenhancement device 10 in the exhaust pipe 2. In this regard, embodimentsof the present invention may be configured to reduce reversion in theengine and the exhaust system. Since the reversion of exhaust gasses(caused, for example, by valve overlap during the engine cycle) dilutesthe charge entering the combustion chamber, reducing the amount ofreversion generally increases the horsepower and/or the responsivenessof the engine. Therefore, by installing an exhaust enhancement device 10that is configured to reduce reversion of exhaust gasses in the exhaustpipe, the rider will often experience improved throttle response, adeeper sound, more midrange power, and more torque than the rider wouldhave experienced without the exhaust enhancement device 10 installed inthe exhaust pipe 2.

FIGS. 2 a and 2 b illustrate a perspective sectional view and aperspective exploded view, respectively, of an exhaust enhancementdevice 10 in accordance with an embodiment of the present invention. Asillustrated in FIGS. 2 a and 2 b, the exhaust enhancement device 10includes a cylindrical tubular body portion 20 and a frustoconicalscreen 30.

In the illustrated embodiment, the cylindrical tubular body portion 20has two cylindrical end portions 24 and 25 on either side of a reduceddiameter center chamber portion 22. The cylindrical tubular body portion20 has a longitudinal axis 15 extending through the center of thecylindrical portions 24 and 25. The two cylindrical end portions 24 and25 are generally configured to have an outside diameter that isapproximately equal to or just less than the inside diameter of theexhaust pipe 2 for which the exhaust enhancement device 10 is designed.In this way, the exhaust from the exhaust pipe 2 is forced through theexhaust enhancement device 10 when the exhaust enhancement device 10 isinstalled inside the exhaust pipe 2.

For example, in an exemplary embodiment, a 1.75-inch diameter tube iscut to a length of approximately 4.5 inches to use in the formation ofthe cylindrical tubular body portion 20. Each end of the tubing may thenbe swaged or expanded to various diameters (dependent on the exhaustpipe 2 into which it will be installed) to form the cylindrical endportions 24 and 25 of substantially uniform diameter, leaving thereduced diameter center chamber portion 22 of approximately 2 inches inlength and 1.75 inches in outside diameter. In an exemplary embodiment,the cylindrical tubular body portion 20 is made from high carbon steeltubing and is dipped in a black oxide solution to heat treat thecylindrical portion 20 and to make it more rust and corrosion resistant.It should be noted that the dimensions described herein are merelyexamples of dimensions that may be typical for an exhaust enhancementdevice configured for a typical exhaust pipe. The actual dimensions(e.g., the length and diameter of the cylindrical portion 20) of theexhaust enhancement device 10 may depend on the particular exhaust pipe2 in which the exhaust enhancement device 10 is to be installed.

As illustrated in FIGS. 2 a and 2 b, the cylindrical tubular bodyportion 20 may include an anti-reversion member 40 located within thecylindrical portion 20. The anti-reversion member 40 located in theenhancer 10 generally acts to create a vortex which allows the exhaustgases to exit the pipe more efficiently and helps lessen reversion. Asdescribed above, lessening any reversion in the exhaust system mayincrease the horsepower and the responsiveness of the engine.

In the illustrated embodiment, the anti-reversion member 40 includes acircular member 42 centrally located within the cylindrical portion 20.The circular member 42 may be, for example, a flat washer-like piece ofmetal having a central opening 43. A shaft 44 may be used to couple thecircular member 42 to an inside wall of the cylindrical portion 20. Inan exemplary embodiment, the shaft is configured to hold the circularmember 42 such that the circular member 42 is oriented in a planeextending perpendicular to the longitudinal axis 15 of the cylindricalportion 20. The circular member 42 may also be oriented such that thecenter of the central opening 43 is located substantially coincidentwith the longitudinal axis 15 of the cylindrical portion 20.

As illustrated in FIG. 2 a, in one embodiment the anti-reversion member40 is disposed within the cylindrical end portion 25 located oppositethe conical portion 30. As such, the anti-reversion member 40 may bedisposed on the upstream end or the downstream end of the cylindricalportion 20 depending upon the orientation of the exhaust enhancementdevice 10 in the exhaust pipe 2. In other embodiments, theanti-reversion member 40 may be disposed within the cylindrical endportion 24 located on the same side of the cylindrical portion 20 as theconical portion 30. Additionally or alternatively, the anti-reversionmember 40 may be disposed within the center chamber portion 22 of thecylindrical portion 20. In still other embodiments, the exhaustenhancement device 10 may be used without an anti-reversion member 40disposed in the cylindrical portion 20, or, in some embodiments, theexhaust enhancement device 10 may have a plurality of anti-reversionmembers 40 of the same or different sizes located at various placeswithin the cylindrical portion 20.

In some embodiments of the present invention, the cylindrical tubularbody portion 20 is comprised of an embodiment of the exhaust enhancementdevice described in co-owned U.S. Pat. No. 6,848,252 or co-pending U.S.patent application Ser. No. 11/005,655, which are incorporated herein byreference. Similarly, the anti-reversion member 40 of embodiments of thepresent invention may be configured in a manner similar to thebaffling/anti-reversion pieces described in these co-owned references.

As illustrated in FIGS. 2 a and 2 b, the frustoconical screen 30 of theexhaust enhancement device 10 may be coupled to the cylindrical end 24of the cylindrical portion 20. In the illustrated embodiment, thefrustoconical screen 30 has a circular cross-section that reduces indiameter as the cross-section is located further from the end of thecylindrical portion 20. In other words, the walls of the conical portion30 generally converge in a funnel-like manner as they extend away fromthe cylindrical portion 20. In the illustrated embodiment, the conicalportion 30 has a longitudinal axis that is defined by an imaginary linedrawn through the center of the circular cross-sections. In theillustrated embodiment, the walls of the conical portion 30 taperuniformly on all sides such that a longitudinal axis of the conicalportion is coincident with the longitudinal axis 15 of the cylindricalportion 20.

At one end (e.g., the “base” end of the conical portion), thecross-section of the conical portion 30 has an outside diameter that isapproximately equal to or slightly less than the inside diameter of thecylindrical end 24 of the cylindrical portion 20. In the illustratedembodiment, the conical portion 30 has a cylindrical end 31 having anoutside diameter approximately equal to the inside diameter of thecylindrical end 24 so that conical portion 30 may be coupled to thecylindrical portion 20 by coupling the cylindrical end 31 of the conicalportion 30 to the cylindrical end 24 of the cylindrical portion 20. Atthe other end of the conical portion 30, the conical portion 30typically has an opening 32 for permitting exhaust to traveltherethrough. In this regard, the conical portion 30 generally has afrusto-conical shape. In addition to the opening 32 in the end of theconical portion 30, the conical portion 30 may have a plurality of otheropenings or holes in the walls of the conical portion 30 that alsopermit exhaust to travel therethrough. In this regard, in oneembodiment, the conical portion 30 is perforated with an array of holesand may be manufactured, for example, from a metallic foraminous screen.As with the cylindrical portion 20, the conical portion 30 may be dippedin or otherwise coated with a black oxide solution to heat treat theconical portion 20 and to make it more rust and corrosion resistant.

As described above, the conical portion 30 may be coupled to thecylindrical portion 20 by coupling the conical portion's cylindrical end31 to the cylindrical portion 20. In this regard, in one embodiment theoutside surface of the conical portion's cylindrical end 31 is welded,soldered, or otherwise adhered to the inside surface of the cylindricalend 24 of the cylindrical portion 20. In other embodiments, a screw orbolt is used to couple the cylindrical end 31 of the conical portion 30to the cylindrical portion 20. In other embodiments, the cylindrical end31 of the conical portion 30 has a diameter that is greater than the endof the cylindrical portion 20 such that the inside surface of thecylindrical end 31 of the conical portion 30 may be coupled to theoutside surface of the cylindrical portion 20. In still otherembodiments, the conical portion 30 may not have a cylindrical end 31and may be coupled to the cylindrical portion 20 in other ways apparentto a person skilled in the art in view of this disclosure.

As illustrated in FIGS. 2 a and 2 b, the conical portion 30 may includean anti-reversion member 45 located within the conical portion 30. Likethe anti-reversion member 40, described above, the anti-reversion member45 may act to reduce reversion of exhaust gasses. As described above,lessening the reversion in the exhaust system may increase thehorsepower and the responsiveness of the engine.

In the illustrated embodiment, the anti-reversion member 45 is embodiedas a circular member 47 centrally located within the conical portion 30.The circular member 47 may be, for example, a flat washer-like piece ofmetal having a central opening 48. In the illustrated embodiment, thecircular member 47 is positioned in the conical portion 30 such that thecircular member 47 is perpendicular to the longitudinal axis 15 of theconical portion 30. As also illustrated in FIG. 2 a, the circular member47 may be positioned at a location in the conical portion 30 where theoutside diameter of the circular member 47 is approximately equal to theinside diameter of the frustoconical screen's cross-section. In such anembodiment, the circular member 47 may be coupled to the conical portion30 by welding, soldering, or otherwise adhering the outside edge of thecircular member 47 to the inside surface of the conical portion 30. Asillustrated in FIGS. 2 a and 2 b, the circular member 47 may be orientedsuch that the center of the central opening 48 is located substantiallycoincident with the longitudinal axis 15 of the conical portion 30.

In other embodiments of the present invention, other means may be usedto couple the circular member 47 to the conical portion 30 and thecircular member 47 may be located and positioned differently in theconical portion 30. For example, in one embodiment, a shaft may be usedto couple the circular member 47 to an inside wall of the conicalportion 30. In some embodiments, the conical portion 30 may beconfigured with more than one anti-reversion member 45 located therein,while, in other embodiments, the conical portion 30 may be used withoutan anti-reversion member 45.

FIGS. 3 a and 3 b illustrate a perspective sectional view and anexploded view, respectively, of an exhaust enhancement device 110 inaccordance with another embodiment of the present invention. Thisembodiment of the present invention is generally similar to theembodiment depicted in FIGS. 2 a and 2 b in that the exhaust enhancementdevice 110 includes a cylindrical tubular body portion 120 having afrustoconical screen 130 extending therefrom. The exhaust enhancementdevice also has an anti-reversion member 140 located within thecylindrical portion 120. As in the embodiments described above, theanti-reversion member 140 may include a flat circular member 142 havinga circular central opening 143. The anti-reversion member 140 may beconfigured such that circular member 142 is positioned perpendicular tothe longitudinal axis 115 of the cylindrical portion 120. The circularmember 142 may also be positioned such that the center of the centralopening 143 is located substantially coincident with the longitudinalaxis 115. A shaft 144 may be used to couple the circular member 142 toan inside wall of the cylindrical portion 120.

The embodiment of the exhaust enhancement device 110 depicted in FIGS. 3a and 3 b differs from the embodiment previously described with respectto FIGS. 2 a and 2 b primarily in that the tubular body of thecylindrical tubular body portion 120 is of uniform diameter throughout.In general, the diameter of the cylindrical tubular body portion 120 isapproximately equal to or just less than the inside diameter of theexhaust pipe 2 for which the exhaust enhancement device 110 is designed.In this way, the exhaust from the exhaust pipe 2 is forced through theexhaust enhancement device 110 when the exhaust enhancement device 110is installed inside the exhaust pipe 2.

FIGS. 3 a and 3 b also illustrate an embodiment of the exhaustenhancement device where only one flat circular member 142 is positionedwithin the path of the exhaust gasses. In other embodiments, however,such as the embodiment illustrated previously with respect to FIGS. 2 aand 2 b, the exhaust enhancement device 110 may include more than oneflat circular member 142 and the flat circular member 142 may bepositioned within frustoconical screen 130 in addition to or as analternative to a flat circular member being positioned within thecylindrical tubular body portion 120.

FIG. 4 is a cross-sectional view of an exhaust pipe 2 illustrated inFIG. 1 a, the exhaust pipe 2 having an exhaust enhancement device 10disposed therein in accordance with an embodiment of the presentinvention. FIG. 4 illustrates how the exhaust enhancement device 10 maybe coupled to the exhaust pipe 2 in an exemplary embodiment of theinvention. Specifically, one or more holes may be punched in the wallsof the cylindrical tubular body portion 20, such as in the walls of thecylindrical ends 24 or 25 that are adjacent to the exhaust pipe wallswhen the exhaust enhancement device 10 is disposed within the exhaustpipe 2. A weld nut 13 can then be spot welded to the interior surface ofthe cylindrical portion's wall at each punched hole. A correspondinghole can be punched in the exhaust pipe 2 and a bolt 17 can be placedthrough the holes and threaded through the weld nut 13 to secure theexhaust enhancement device 10 within the exhaust pipe 2. Of course,other means of securing the exhaust enhancement device 10 within theexhaust pipe 2 will be apparent to a person skilled in the art in viewof this disclosure.

FIG. 4 also illustrates how an embodiment of the anti-reversion member240 may be coupled to the exhaust enhancement device 10 in accordancewith an embodiment of the invention. In one embodiment, the shaft of theanti-reversion member 240 is made from a threaded screw or bolt 244 andthe flat circular member 242 is made from a washer. For example, a ¼ 20Allen head screw may be used with a 316 stainless steel washer that isheliarc welded to the top of the Allen screw using stainless steel rod.Once the washer is welded to the screw, they may then be polished toharden and smooth them. In the illustrated embodiment, a weld nut 13 iswelded to the interior surface of the wall of the cylindrical tubularbody portion 20 and the threaded shaft 244 of the anti-reversion member240 is threaded into the weld nut 13. When the shaft 244 is threadedinto the weld nut 13 such that the washer is oriented and positioned asdesired within the path of the exhaust gasses, the anti-reversion member240 may be secured in position by tightening a lock nut 18 against theweld nut 13. In one embodiment, holes are punched through thecylindrical portion 20 and/or the exhaust pipe 2 so that the shaft 244can extend therethrough. In such an embodiment, the shaft 244 inconjunction with the holes and the weld nut 13 may be used to secure theexhaust enhancement device 10 within the exhaust pipe 2.

In other embodiments of the present invention, the anti-reversion membermay be fabricated from a single piece of metal and may be welded to thebody of the exhaust enhancement device 10. For example, in oneembodiment, the anti-reversion piece may be fabricated from a standardeye-type electrical terminal of the kind commonly used for connecting anautomotive battery cable to a battery. The flat circular-shaped portionof the anti-reversion piece is formed by the eye portion of the terminaland shaft portion of the anti-reversion is formed by the lug portion ofthe terminal which, when used as an electrical connector, is designed tobe crimped onto the battery cable. The one end of the shaft portion maythen be welded to the interior of the tubular body. The opposite end ofthe shaft portion terminates in the above-noted flat circular portion,which is position centrally of the cylindrical tubular body. Moreparticularly, the flat circular shaped portion is in the shape of a flatwasher having a central opening with a center located substantiallycoincident with the longitudinal axis of the tubular body. FIGS. 2 athrough 3 b illustrate anti-reversion members 40 and 140 that aregenerally of the type formed from an eye-type electrical terminal, inaccordance with one embodiment of the invention.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. An exhaust enhancement device for a motorcycle exhaust pipecomprising: a cylindrical tubular body portion configured to be receivedwithin a motorcycle exhaust pipe for receiving the flow of exhaust gasestherethrough, said body portion having first and second open oppositeends and a cylindrical wall extending therebetween; a formanious screenextending from said first end of the cylindrical tubular body portion,said screen having a frustoconical configuration converging as itextends away from the body portion and defining an open first end of adiameter generally corresponding to the diameter of said first end ofthe body portion and an open opposite second end of a smaller diameter;and at least one obstruction positioned within the cylindrical tubularbody portion or the frustoconical screen in the flow path of exhaustgases passing through the enhancement device.
 2. The exhaust enhancementdevice of claim 1, wherein the at least one obstruction comprises a flatcircular member.
 3. The exhaust enhancement device of claim 2, whereinthe flat circular member is oriented in a plane perpendicular to thelongitudinal axis of the cylindrical tubular body portion.
 4. Theexhaust enhancement device of claim 3, wherein the flat circular memberhas a central opening and is positioned coaxially of the longitudinalaxis of the cylindrical body portion.
 5. The exhaust enhancement deviceof claim 4, wherein the flat circular member is positioned within thefrustoconical screen.
 6. The exhaust enhancement device of claim 5,wherein outer peripheral edges of the flat circular member are connectedto the interior surface of the frustoconical screen to secure the flatcircular member in place.
 7. The exhaust enhancement device of claim 4,wherein the flat circular member is positioned within the cylindricaltubular body portion.
 8. The exhaust enhance device of claim 7,including a shaft having a first end connected to the flat circularmember and a second end connected to the interior surface of thecylindrical wall of the tubular body portion.
 9. The exhaust enhancementdevice of claim 1, wherein the at least one obstruction comprises afirst flat circular member oriented in a plane perpendicular to thelongitudinal axis of the cylindrical tubular body portion and positionedwithin the frustoconical screen and a second flat circular memberoriented in a plane perpendicular to the longitudinal axis of thecylindrical tubular body portion and positioned within the cylindricaltubular body portion.
 10. The exhaust enhancement device of claim 9,wherein said first and second flat circular members each have a centralopening and are positioned coaxially of the longitudinal axis of thecylindrical body portion.
 11. The exhaust enhancement device of claim 1,wherein the frustoconical screen includes a cylindrical first endportion adjacent said open first end which is received within andsecured to said cylindrical wall of said cylindrical tubular bodyportion and a frustoconical tapering second portion extending from saidfirst end portion to said open second end of the frustoconical screen.12. The exhaust enhancement device of claim 1, wherein an outsidediameter of the cylindrical tubular body portion is approximately equalto the inside diameter of the motorcycle exhaust pipe.
 13. The exhaustenhancement device of claim 1, wherein the wall of said cylindricaltubular body portion includes a reduced-diameter center chamber betweensaid first and second opposite ends.
 14. The exhaust enhancement deviceof claim 13, wherein the at least one obstruction comprises a flatcircular member oriented in a plane perpendicular to the longitudinalaxis of the cylindrical tubular body portion and located adjacent one ofsaid ends.
 15. A motorcycle exhaust system comprising: an exhaust pipefor expelling exhaust from an engine; a cylindrical tubular body portionreceived within said exhaust pipe for receiving the flow of exhaustgases therethrough, said body portion having first and second openopposite ends and a cylindrical wall extending therebetween; aformanious screen extending from said first end of the cylindricaltubular body portion, said screen having a frustoconical configurationconverging as it extends away from the body portion and defining an openfirst end of a diameter generally corresponding to the diameter of saidfirst end of the body portion and an open opposite second end of asmaller diameter; and at least one obstruction positioned within thecylindrical tubular body portion or the frustoconical screen in the flowpath of exhaust gases passing through the enhancement device.
 16. Theexhaust system of claim 15, wherein the at least one obstructioncomprises a flat circular member oriented in a plane perpendicular tothe longitudinal axis of the cylindrical tubular body portion.
 17. Theexhaust system of claim 16, wherein the flat circular member has acentral opening and is positioned coaxially of the longitudinal axis ofthe cylindrical body portion.
 18. The exhaust system of claim 15,wherein the open second end of the frustoconical screen is orientedtoward an engine end of the exhaust pipe.
 19. The exhaust system ofclaim 15, wherein the open second end of the frustoconical screen isoriented toward an exit end of the exhaust pipe.
 20. The exhaust systemof claim 15, wherein the outside diameter of at least a portion of thecylindrical tubular body portion corresponds approximately to the insidediameter of the exhaust pipe.